Field works. Example 6.

Delineate the boundaries between limestone and dolomite

Electrical tomography survey was conducted to delineate the boundaries between limestone and dolomite. On geoelectric model the high-resistivity layer is clearly visible. This layer associates with dolomite (underlayment of limestone). Dolomite is reflected by lower porosity and higher resistivity values than limestone. 


Resistivity section by ERT results

The low-resistivity marl underlies the dolomite. The upper layer thickness of the model is 1 m. This layer corresponds to the near-surface rocks of different composition. Deeper, there is a layer of clay, which has the resistivity values from 60 to 100 Ohm-m. The thickness of this layer varies from 2 to 4 m. Comparison of geoelectric model and borehole data shows that limestone layer (the thickness is 6 m) is reflected by high resistivity values. The depth to the top of the layer is around 4-6 m. Deeper, there is dolomite of a much higher resistivity. Resistivity values decrease with the depth 120-460 Ohm-m because of low-resistivity marl underlies the dolomite. Electrotomography data were processed with the use of ZondRes2D.